1. Field of the Invention
The present invention relates to an apparatus and a method for charging a portable terminal using a battery. More particularly, the present invention relates to an apparatus and a method for charging a terminal by using a detachable device.
2. Description of the Related Art
A growing trend for portable terminals is to evolve from a terminal performing a single function, such as a portable cell phone, a camera or an audio player, to a terminal performing multiple functions. In other words, portable terminals may perform various multiple functions such as data communication, displaying or playing multimedia content, a camera, or other similar functions. The portable terminal may be a terminal such as a smart phone, a tablet, a netbook, or other similar portable electronic devices. By using such a portable terminal, a user may continuously perform various functions and, thus, may continuously execute an application that consumes a large amount of power. In this case, battery power consumption of the portable terminal is increased, thereby limiting an operation time of the portable terminal. Therefore, it is necessary to provide a function for enabling the portable terminal to operate for a long period of time. To this end, the portable terminal generally has an internal configuration comprising low power consumption devices. Also, an auxiliary battery may be used when connected to the portable terminal.
FIG. 1 is a view illustrating a configuration of a related art portable terminal including, a master device and a detachable device.
Referring to FIG. 1, a detachable device 10 includes a battery 13 that has a rated voltage of 3.7 volts (V). Also, an input port 11 for receiving data or a power supply from an external device receives an external power of 5 V, which is reduced by a charging unit 12 to a rated voltage of 4.2 V and is used to charge the battery 13. In addition, an output port 15 of the detachable device 10 is connected to an input port 21 of a master device 20 when a 5 V power supply is outputted and inputted through a V_BUS terminal that is a power supply terminal. Therefore, the detachable device 10 uses a DC/DC booster 14 for boosting a 4V power supply of a battery 13 to 5V between the battery 13 and the output port 15. In other words, the DC/DC booster 14 is used to boost the 4 V power supply outputted from the battery 13 to 5 V and output the boosted voltage to the master device 20.
When the detachable device 10 is charged as described above, an external 5 V power supply is inputted through input port 11, which may be a Universal Serial Bus (USB) port or an adaptor, and is reduced to 4.2 V through the charging unit 12 in order to charge the battery 13. When connected to the master device 20, the 4 V power supplied by the battery 13 is boosted to 5 V through the DC/DC booster 14 connected to the battery 13, and the boosted voltage is provided to the master device 20. Accordingly, when using the detachable device 10, as described above in the related art, a problem is caused such that an efficiency is decreased (by, for example, 90%) due to the DC/DC booster 14. Here, when an input voltage Vin of the DC/DC booster 14 is 4 V, an output voltage Vout is 5 V, and an output current Iout is 1 A, wherein the input current Iin is 1.25 A if the efficiency is 100% and about 1.4 A if the efficiency is 90%. Thus, power consumption of the battery 13 is increased by the DC/DC booster 14 connected to the battery 13.